The following disclosure is based on German Application No. 19853892.8, filed on Nov. 23, 1998, which is incorporated into this application by reference.
The invention relates to new and useful improvements in electronic scales. More particularly, the invention relates to electronic scales having a line powered voltage supply that preferably includes a transformer and a downstream rectifier and a charging capacitor. Such electronic scales also preferably have a line switch between the transformer and the power line connection, and have at least two operating states. Specifically, all the electronic components are supplied with voltage in the first, or normal, operating state. In the second or standby operating state, only the essential heat-generating components are switched on, while the display and components susceptible to deterioration over time are switched off.
Scales of this type are disclosed, for example, in the German Patent document DE 29 22 848 C2. According to this reference, the standby operating state serves the purpose of maintaining the approximate temperature distribution in the scales that exists in the normal operating state, while nonetheless switching off the display and those components that are susceptible to deterioration over time. The reason for this is to ensure that even immediately after the switchover from the standby operating state into the normal operating state, the scales operate with full accuracy, without the occurrence of deviations arising due to a substantially different temperature distribution inside the scales. This conventional art suffers from a disadvantage, however, in that the energy consumption during the standby operating state, although not being high, does add up to substantial values because of the long period of time in which the scales are usually operated in the standby operating state.
It is therefore an object of the invention to further reduce the energy consumption of electronic scales of the type mentioned above. It is a further object of the invention to reduce energy consumption while nonetheless avoiding the detrimental effects on the scale""s accuracy that would result if the heat-generating components were switched off from the supply voltage during standby.
According to one formulation, the invention is directed to an electronic scale that includes a line powered voltage supply, a line switch, a display, a clock module, and a further, separate voltage supply. The line powered voltage supply has a transformer and, downstream from the transformer, a rectifier and a charging capacitor. The line switch is arranged between the transformer and an outlet to the line, and is an electrically operable switch. The scale has a normal operating state, in which all electronic components of the scale are supplied with voltage, and a standby operating state, in which heat-generating components are supplied with voltage while the display and other components susceptible to deterioration over time are not supplied with voltage. The separate voltage supply is independent of the line powered voltage supply and supplies the clock module with voltage. The scale has, in addition to the normal operating state and the standby state, a further operating state, in which the line switch is open. After expiration of a prescribed time or at a prescribed time of day, the clock module automatically terminates the further operating state and switches the scale over into the normal operating state or the standby operating state.
According to the invention, the objects of the invention are achieved by virtue of the line switch being an electrically operable switch, and a separate voltage supply is provided, which is independent of the line powered voltage supply and which supplies at least one clock module with voltage. In addition to the normal operating state and the standby state, there is provided a further operating state (a sleep mode) in which the line switch is open. After expiration of a prescribed time and/or at a prescribed time of day, the clock module automatically terminates the further operating state (the sleep mode) and switches over into the normal operating state or the standby operating state.
During the sleep mode, the normal electronic system of the scale is therefore completely disconnected from the main power grid, and the separate voltage supply keeps only a xe2x80x9cminimal electronic systemxe2x80x9d in the form of a clock module functional, so that the normal line powered voltage supply is switched on again automatically after expiration of the prescribed time or at the prescribed time of day. The invention in this case utilizes the fact that most electronic scales are operated in a fixed temporal rhythm. It then suffices, for example, to terminate the sleep mode at some given time, e.g., 1.5 hours before the usual time that operation of the scales is begun. The scales then switch over into, for example, the standby operating state so that at the start of operation the scales have achieved their state of thermal equilibrium and thus their full accuracy. The separate voltage supply can advantageously consist of or include either a rechargeable energy storage mechanism (rechargeable battery or capacitor of high capacitance) or of a rectifier circuit, and a charging capacitor, which is connected directly to the two poles of the outlet to the power source via two capacitors.